Transcript Slide 1

S1 Science
Acids and Bases
REVISION
NEW LEARNING
I have investigated different
water samples from the
environment and explored
methods that can be used to
clean and conserve water and
I am aware of the properties
and uses of water.
Having taken part in practical
activities to compare the
properties of acids and bases,
I have demonstrated ways of
measuring and adjusting pH
and can describe the
significance of pH in everyday
life.
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Explain what the pH scale is
Learning what pH is used to measure. Colouring in a pH
scale to show the different values. Watch a video to show
us how to measure pH
What are acids and bases?
You may not have heard
of bases but you’ve
probably heard of acids
Acid – a substance with a pH less than 7
Bases – a substance with a pH more than 7
The pH Scale
• The pH number of a substance is linked
to how concentrated an acid or base is
• Water is neither acid nor base so is pH
7, in the middle
The pH scale extends from pH 1 to pH 14.
To find out pH you must use an indicator like UNIVERSAL
INDICATOR.
Most indicators change colour dependent on pH.
The diagram below shows how colour with universal indicator links to
pH number and how acidic or alkaline a substance is.
What is an indicator?
• Indicators work simply by changing
colour when they come into contact with
certain substances
• They are used to show if a substance is
acidic, alkaline or neutral
Indicators
• Indicators in general come from plant
materials .e.g. beetroot, blackcurrants
or brightly coloured flower petals
• Universal indicator is a mixture of
several indicators.
• How to test acids and alkalis
Explain what the pH scale is
Learning what pH is used to measure. Colouring in a pH
scale to show the different values. Watch a video to show
us how to measure pH
S1 Science
Acids and Bases
REVISION
NEW LEARNING
I have investigated different
water samples from the
environment and explored
methods that can be used to
clean and conserve water and
I am aware of the properties
and uses of water.
Having taken part in practical
activities to compare the
properties of acids and bases,
I have demonstrated ways of
measuring and adjusting pH
and can describe the
significance of pH in everyday
life.
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Starter Questions
• What does the pH scale measure?
It measures how acidic a substance is
• What colour is a neutral solution on the
pH scale?
• Green
Measure how acidic substances are.
Learning what the pH of a substance is and doing
An experiment to measure the pH of some everyday
substances.
What is a hazard?
• A hazard is something that can cause
you danger
• We should use symbols to represent
hazards because it’s easy to understand
• Symbols are brightly coloured so that
you notice them
Testing the pH of substances
• For liquids use a dropper to
put a few drops on a dimple
tray
• For solids use a spatula
• Add 3 drops of universal
indicator
• Do not stir solids – this can
change the colour
• Note down the colour and compare this
to the chart you’ve been given
• Acids – red, orange, yellow
• Neutral – green
• Alkali – dark green, blue, purple
Substance
Colour
Acid, neutral or alkali
• http://www.bgfl.org/bgfl/custom/resources_
ftp/client_ftp/ks3/science/acids/
• Test the pH of common household
substances
Measure how acidic substances are.
Learning what the pH of a substance is and doing
An experiment to measure the pH of some everyday
substances.
S1 Science
Acids and Bases
REVISION
NEW LEARNING
I have investigated different
water samples from the
environment and explored
methods that can be used to
clean and conserve water and
I am aware of the properties
and uses of water.
Having taken part in practical
activities to compare the
properties of acids and bases,
I have demonstrated ways of
measuring and adjusting pH
and can describe the
significance of pH in everyday
life.
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Starter Questions
• Name a household acid
Vinegar, tomato sauce, lemon juice etc.
• Name a household base
• Bleach, toothpaste, bicarbonate of soda
Describe how household acids are different from
laboratory acids
Learning the names of some common laboratory
acids, carry out an experiment with these acids
Acids
• A household acid is something that we
find at home e.g. vinegar, tomato sauce,
orange juice etc.
• A laboratory acid is one that is used in
the laboratory. Common laboratory
acids include hydrochloric acid,
sulphuric acid and nitric acid
Experiment
• Test the pH of some household acids
and compare them to the pH of
laboratory acids
Substance
pH number
Questions
• Generally which is more acidic,
household acids or laboratory acids?
• You put vinegar on your chips, but would
you put hydrochloric acid (or any
laboratory acid) on food and eat it?
Explain your answer.
Describe how household acids are different from
laboratory acids
Learning the names of some common laboratory
acids, carry out an experiment with these acids
Starter Questions
• Is vinegar an acid or base?
• Is cola an acid or base?
S1 Science
Acids and Bases
REVISION
NEW LEARNING
I have investigated different
water samples from the
environment and explored
methods that can be used to
clean and conserve water and
I am aware of the properties
and uses of water.
Having taken part in practical
activities to compare the
properties of acids and bases,
I have demonstrated ways of
measuring and adjusting pH
and can describe the
significance of pH in everyday
life.
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Describe what a base is, explain that an alkali is a
special type of base
Learning the names of some common laboratory bases, carry
out an experiment with these bases
Bases
• Most of you will have heard of acids
before
• How many of you have heard of bases?
• They are used everyday too
Household bases
Some cleaning products have a pH
MORE than seven. This means
that they are a base
• Oven cleaner
• Bleach
You wear gloves because bases
can be corrosive just like acids
Common Bases
• Test the pH of some household bases
and compare them to the pH of
laboratory bases
Substance
pH number
What is an alkali?
• An alkali also has a pH of more than
seven
• How is it different from a base?
• Both have a pH of more than seven, but
alkalis also dissolve in water
Alkali
Base
Also dissolves
in water
pH more than 7
Try these two bases…
• Add half a spatula of sodium oxide to a
test tube then add water – what happens?
• Add universal indicator and note the colour
• Next add half a spatula of sodium
carbonate to a test tube then add water –
what happens?
• Add universal indicator and note the colour
Questions
• Explain what happened when you added
water to the sodium oxide
• Can we call this an alkali as well as a
base?
• Explain what happened when you added
water to the sodium carbonate
• Can we call this an alkali as well as a
base?
Put these alkalis
into a table.
Decide if they
Are household
alkalis or
laboratory (lab)
alkalis
Alkalis
sodium hydroxide
lime water
ammonia solution
bicarbonate of soda
oven cleaner
dishwasher powder
bleach
hard soap
Household
oven cleaner
dishwasher powder
bleach
hard soap
Lab
sodium hydroxide
lime water
ammonia solution
bicarbonate of soda